[v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

[PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Zheng Zengkai 1 year, 3 months ago

As suggested by Marc and Lorenzo, first we need to check whether the
platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
de-referencing what it points at to detect the length of the platform
timer struct and then check that the length of current platform_timer
struct is also valid, i.e. the length is not zero and within gtdt_end.
Now next_platform_timer() only checks against gtdt_end for the entry of
subsequent platform timer without checking the length of it and will
not report error if the check failed and the existing check in function
acpi_gtdt_init() is also not enough.

Modify the for_each_platform_timer() iterator and use it combined with
a dedicated check function platform_timer_valid() to do the check
against table length (gtdt_end) for each element of platform timer
array in function acpi_gtdt_init(), making sure that both their entry
and length actually fit in the table.

Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Co-developed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
---
Changes in v4:
- remove the tmp pointer to make the code more concise.

Changes in v3:
- based on Marc's patch and reuse the for_each_platform_timer() loop
Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@huawei.com/

Changes in v2:
- Check against gtdt_end for both entry and len of each array element
Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@huawei.com/

Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@huawei.com/

Link to previous related patches:
https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@huawei.com/
https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
---
 drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
index c0e77c1c8e09..d7c4e1b9915b 100644
--- a/drivers/acpi/arm64/gtdt.c
+++ b/drivers/acpi/arm64/gtdt.c
@@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
 
 static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
 
-static inline __init void *next_platform_timer(void *platform_timer)
+static __init bool platform_timer_valid(void *platform_timer)
 {
 	struct acpi_gtdt_header *gh = platform_timer;
 
-	platform_timer += gh->length;
-	if (platform_timer < acpi_gtdt_desc.gtdt_end)
-		return platform_timer;
+	return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
+		platform_timer < acpi_gtdt_desc.gtdt_end &&
+		gh->length != 0 &&
+		platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
+}
+
+static __init void *next_platform_timer(void *platform_timer)
+{
+	struct acpi_gtdt_header *gh = platform_timer;
 
-	return NULL;
+	return platform_timer + gh->length;
 }
 
 #define for_each_platform_timer(_g)				\
-	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
+	for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
 	     _g = next_platform_timer(_g))
 
 static inline bool is_timer_block(void *platform_timer)
@@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
 {
 	void *platform_timer;
 	struct acpi_table_gtdt *gtdt;
+	int cnt = 0;
 
 	gtdt = container_of(table, struct acpi_table_gtdt, header);
 	acpi_gtdt_desc.gtdt = gtdt;
@@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
 		return 0;
 	}
 
-	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
-	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
+	acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
+	for_each_platform_timer(platform_timer)
+		cnt++;
+
+	if (cnt != gtdt->platform_timer_count) {
+		acpi_gtdt_desc.platform_timer = NULL;
 		pr_err(FW_BUG "invalid timer data.\n");
 		return -EINVAL;
 	}
-	acpi_gtdt_desc.platform_timer = platform_timer;
+
 	if (platform_timer_count)
 		*platform_timer_count = gtdt->platform_timer_count;
 
-- 
2.20.1

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Catalin Marinas 1 year, 3 months ago

On Wed, 16 Oct 2024 17:54:58 +0800, Zheng Zengkai wrote:
> As suggested by Marc and Lorenzo, first we need to check whether the
> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
> de-referencing what it points at to detect the length of the platform
> timer struct and then check that the length of current platform_timer
> struct is also valid, i.e. the length is not zero and within gtdt_end.
> Now next_platform_timer() only checks against gtdt_end for the entry of
> subsequent platform timer without checking the length of it and will
> not report error if the check failed and the existing check in function
> acpi_gtdt_init() is also not enough.
> 
> [...]

Applied to arm64 (for-next/misc), thanks!

[1/1] ACPI: GTDT: Tighten the check for the array of platform timer structures
      https://git.kernel.org/arm64/c/263e22d6bd1f

-- 
Catalin

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Hanjun Guo 1 year, 3 months ago

On 2024/10/16 17:54, Zheng Zengkai wrote:
> As suggested by Marc and Lorenzo, first we need to check whether the
> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
> de-referencing what it points at to detect the length of the platform
> timer struct and then check that the length of current platform_timer
> struct is also valid, i.e. the length is not zero and within gtdt_end.
> Now next_platform_timer() only checks against gtdt_end for the entry of
> subsequent platform timer without checking the length of it and will
> not report error if the check failed and the existing check in function
> acpi_gtdt_init() is also not enough.
> 
> Modify the for_each_platform_timer() iterator and use it combined with
> a dedicated check function platform_timer_valid() to do the check
> against table length (gtdt_end) for each element of platform timer
> array in function acpi_gtdt_init(), making sure that both their entry
> and length actually fit in the table.
> 
> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Co-developed-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Marc Zyngier <maz@kernel.org>

Nit: since there is a "Co-developed-by:" for Marc, the
"Signed-off-by:" can be removed. The rest of the patch looks
good to me.

I did a test again Kunpeng ARM sever and no regressions,
hopefully will not trigger firmware bugs for other
platforms.

Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>

Thanks
Hanjun

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Hanjun Guo 1 year, 3 months ago

On 2024/10/19 14:41, Hanjun Guo wrote:
> On 2024/10/16 17:54, Zheng Zengkai wrote:
>> As suggested by Marc and Lorenzo, first we need to check whether the
>> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
>> de-referencing what it points at to detect the length of the platform
>> timer struct and then check that the length of current platform_timer
>> struct is also valid, i.e. the length is not zero and within gtdt_end.
>> Now next_platform_timer() only checks against gtdt_end for the entry of
>> subsequent platform timer without checking the length of it and will
>> not report error if the check failed and the existing check in function
>> acpi_gtdt_init() is also not enough.
>>
>> Modify the for_each_platform_timer() iterator and use it combined with
>> a dedicated check function platform_timer_valid() to do the check
>> against table length (gtdt_end) for each element of platform timer
>> array in function acpi_gtdt_init(), making sure that both their entry
>> and length actually fit in the table.
>>
>> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>> Co-developed-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
> 
> Nit: since there is a "Co-developed-by:" for Marc, the
> "Signed-off-by:" can be removed.

Forget about this comment, the guide from submit patches needs
the Signed-off-by:, sorry for the noise.

Thanks
Hanjun

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Lorenzo Pieralisi 1 year, 3 months ago

On Wed, Oct 16, 2024 at 05:54:58PM +0800, Zheng Zengkai wrote:
> As suggested by Marc and Lorenzo, first we need to check whether the
> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
> de-referencing what it points at to detect the length of the platform
> timer struct and then check that the length of current platform_timer
> struct is also valid, i.e. the length is not zero and within gtdt_end.
> Now next_platform_timer() only checks against gtdt_end for the entry of
> subsequent platform timer without checking the length of it and will
> not report error if the check failed and the existing check in function
> acpi_gtdt_init() is also not enough.
> 
> Modify the for_each_platform_timer() iterator and use it combined with
> a dedicated check function platform_timer_valid() to do the check
> against table length (gtdt_end) for each element of platform timer
> array in function acpi_gtdt_init(), making sure that both their entry
> and length actually fit in the table.
> 
> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Co-developed-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
> ---
> Changes in v4:
> - remove the tmp pointer to make the code more concise.
> 
> Changes in v3:
> - based on Marc's patch and reuse the for_each_platform_timer() loop
> Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@huawei.com/
> 
> Changes in v2:
> - Check against gtdt_end for both entry and len of each array element
> Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@huawei.com/
> 
> Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@huawei.com/
> 
> Link to previous related patches:
> https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@huawei.com/
> https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
> ---
>  drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)

Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
> index c0e77c1c8e09..d7c4e1b9915b 100644
> --- a/drivers/acpi/arm64/gtdt.c
> +++ b/drivers/acpi/arm64/gtdt.c
> @@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
>  
>  static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
>  
> -static inline __init void *next_platform_timer(void *platform_timer)
> +static __init bool platform_timer_valid(void *platform_timer)
>  {
>  	struct acpi_gtdt_header *gh = platform_timer;
>  
> -	platform_timer += gh->length;
> -	if (platform_timer < acpi_gtdt_desc.gtdt_end)
> -		return platform_timer;
> +	return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
> +		platform_timer < acpi_gtdt_desc.gtdt_end &&
> +		gh->length != 0 &&
> +		platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
> +}
> +
> +static __init void *next_platform_timer(void *platform_timer)
> +{
> +	struct acpi_gtdt_header *gh = platform_timer;
>  
> -	return NULL;
> +	return platform_timer + gh->length;
>  }
>  
>  #define for_each_platform_timer(_g)				\
> -	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
> +	for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
>  	     _g = next_platform_timer(_g))
>  
>  static inline bool is_timer_block(void *platform_timer)
> @@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>  {
>  	void *platform_timer;
>  	struct acpi_table_gtdt *gtdt;
> +	int cnt = 0;
>  
>  	gtdt = container_of(table, struct acpi_table_gtdt, header);
>  	acpi_gtdt_desc.gtdt = gtdt;
> @@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>  		return 0;
>  	}
>  
> -	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
> +	acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> +	for_each_platform_timer(platform_timer)
> +		cnt++;
> +
> +	if (cnt != gtdt->platform_timer_count) {
> +		acpi_gtdt_desc.platform_timer = NULL;
>  		pr_err(FW_BUG "invalid timer data.\n");
>  		return -EINVAL;
>  	}
> -	acpi_gtdt_desc.platform_timer = platform_timer;
> +
>  	if (platform_timer_count)
>  		*platform_timer_count = gtdt->platform_timer_count;
>  
> -- 
> 2.20.1
>

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Zheng Zengkai 1 year, 3 months ago

Gentle ping.

This patch still can be applied to upstream now.

Thanks!


在 2024/10/16 18:01, Lorenzo Pieralisi 写道:
> On Wed, Oct 16, 2024 at 05:54:58PM +0800, Zheng Zengkai wrote:
>> As suggested by Marc and Lorenzo, first we need to check whether the
>> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
>> de-referencing what it points at to detect the length of the platform
>> timer struct and then check that the length of current platform_timer
>> struct is also valid, i.e. the length is not zero and within gtdt_end.
>> Now next_platform_timer() only checks against gtdt_end for the entry of
>> subsequent platform timer without checking the length of it and will
>> not report error if the check failed and the existing check in function
>> acpi_gtdt_init() is also not enough.
>>
>> Modify the for_each_platform_timer() iterator and use it combined with
>> a dedicated check function platform_timer_valid() to do the check
>> against table length (gtdt_end) for each element of platform timer
>> array in function acpi_gtdt_init(), making sure that both their entry
>> and length actually fit in the table.
>>
>> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>> Co-developed-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
>> ---
>> Changes in v4:
>> - remove the tmp pointer to make the code more concise.
>>
>> Changes in v3:
>> - based on Marc's patch and reuse the for_each_platform_timer() loop
>> Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@huawei.com/
>>
>> Changes in v2:
>> - Check against gtdt_end for both entry and len of each array element
>> Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@huawei.com/
>>
>> Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@huawei.com/
>>
>> Link to previous related patches:
>> https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@huawei.com/
>> https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
>> ---
>>   drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
>>   1 file changed, 20 insertions(+), 9 deletions(-)
> Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index c0e77c1c8e09..d7c4e1b9915b 100644
>> --- a/drivers/acpi/arm64/gtdt.c
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
>>   
>>   static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
>>   
>> -static inline __init void *next_platform_timer(void *platform_timer)
>> +static __init bool platform_timer_valid(void *platform_timer)
>>   {
>>   	struct acpi_gtdt_header *gh = platform_timer;
>>   
>> -	platform_timer += gh->length;
>> -	if (platform_timer < acpi_gtdt_desc.gtdt_end)
>> -		return platform_timer;
>> +	return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
>> +		platform_timer < acpi_gtdt_desc.gtdt_end &&
>> +		gh->length != 0 &&
>> +		platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
>> +}
>> +
>> +static __init void *next_platform_timer(void *platform_timer)
>> +{
>> +	struct acpi_gtdt_header *gh = platform_timer;
>>   
>> -	return NULL;
>> +	return platform_timer + gh->length;
>>   }
>>   
>>   #define for_each_platform_timer(_g)				\
>> -	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
>> +	for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
>>   	     _g = next_platform_timer(_g))
>>   
>>   static inline bool is_timer_block(void *platform_timer)
>> @@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>>   {
>>   	void *platform_timer;
>>   	struct acpi_table_gtdt *gtdt;
>> +	int cnt = 0;
>>   
>>   	gtdt = container_of(table, struct acpi_table_gtdt, header);
>>   	acpi_gtdt_desc.gtdt = gtdt;
>> @@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>>   		return 0;
>>   	}
>>   
>> -	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>> -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
>> +	acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>> +	for_each_platform_timer(platform_timer)
>> +		cnt++;
>> +
>> +	if (cnt != gtdt->platform_timer_count) {
>> +		acpi_gtdt_desc.platform_timer = NULL;
>>   		pr_err(FW_BUG "invalid timer data.\n");
>>   		return -EINVAL;
>>   	}
>> -	acpi_gtdt_desc.platform_timer = platform_timer;
>> +
>>   	if (platform_timer_count)
>>   		*platform_timer_count = gtdt->platform_timer_count;
>>   
>> -- 
>> 2.20.1
>>
> .
>

Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

Posted by Lorenzo Pieralisi 1 year, 3 months ago

[+Catalin/Will]

On Tue, Oct 29, 2024 at 10:16:41PM +0800, Zheng Zengkai wrote:
> 
> Gentle ping.
> 
> This patch still can be applied to upstream now.

Hi Catalin, Will,

this patch is a clean-up - not a fix, it could be merged
for v6.13, please consider it if there is still time.

Thanks,
Lorenzo

> 
> Thanks!
> 
> 
> 在 2024/10/16 18:01, Lorenzo Pieralisi 写道:
> > On Wed, Oct 16, 2024 at 05:54:58PM +0800, Zheng Zengkai wrote:
> > > As suggested by Marc and Lorenzo, first we need to check whether the
> > > platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
> > > de-referencing what it points at to detect the length of the platform
> > > timer struct and then check that the length of current platform_timer
> > > struct is also valid, i.e. the length is not zero and within gtdt_end.
> > > Now next_platform_timer() only checks against gtdt_end for the entry of
> > > subsequent platform timer without checking the length of it and will
> > > not report error if the check failed and the existing check in function
> > > acpi_gtdt_init() is also not enough.
> > > 
> > > Modify the for_each_platform_timer() iterator and use it combined with
> > > a dedicated check function platform_timer_valid() to do the check
> > > against table length (gtdt_end) for each element of platform timer
> > > array in function acpi_gtdt_init(), making sure that both their entry
> > > and length actually fit in the table.
> > > 
> > > Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> > > Co-developed-by: Marc Zyngier <maz@kernel.org>
> > > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > > Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
> > > ---
> > > Changes in v4:
> > > - remove the tmp pointer to make the code more concise.
> > > 
> > > Changes in v3:
> > > - based on Marc's patch and reuse the for_each_platform_timer() loop
> > > Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@huawei.com/
> > > 
> > > Changes in v2:
> > > - Check against gtdt_end for both entry and len of each array element
> > > Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@huawei.com/
> > > 
> > > Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@huawei.com/
> > > 
> > > Link to previous related patches:
> > > https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@huawei.com/
> > > https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
> > > ---
> > >   drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
> > >   1 file changed, 20 insertions(+), 9 deletions(-)
> > Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> > 
> > > diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
> > > index c0e77c1c8e09..d7c4e1b9915b 100644
> > > --- a/drivers/acpi/arm64/gtdt.c
> > > +++ b/drivers/acpi/arm64/gtdt.c
> > > @@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
> > >   static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
> > > -static inline __init void *next_platform_timer(void *platform_timer)
> > > +static __init bool platform_timer_valid(void *platform_timer)
> > >   {
> > >   	struct acpi_gtdt_header *gh = platform_timer;
> > > -	platform_timer += gh->length;
> > > -	if (platform_timer < acpi_gtdt_desc.gtdt_end)
> > > -		return platform_timer;
> > > +	return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
> > > +		platform_timer < acpi_gtdt_desc.gtdt_end &&
> > > +		gh->length != 0 &&
> > > +		platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
> > > +}
> > > +
> > > +static __init void *next_platform_timer(void *platform_timer)
> > > +{
> > > +	struct acpi_gtdt_header *gh = platform_timer;
> > > -	return NULL;
> > > +	return platform_timer + gh->length;
> > >   }
> > >   #define for_each_platform_timer(_g)				\
> > > -	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
> > > +	for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
> > >   	     _g = next_platform_timer(_g))
> > >   static inline bool is_timer_block(void *platform_timer)
> > > @@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
> > >   {
> > >   	void *platform_timer;
> > >   	struct acpi_table_gtdt *gtdt;
> > > +	int cnt = 0;
> > >   	gtdt = container_of(table, struct acpi_table_gtdt, header);
> > >   	acpi_gtdt_desc.gtdt = gtdt;
> > > @@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
> > >   		return 0;
> > >   	}
> > > -	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> > > -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
> > > +	acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> > > +	for_each_platform_timer(platform_timer)
> > > +		cnt++;
> > > +
> > > +	if (cnt != gtdt->platform_timer_count) {
> > > +		acpi_gtdt_desc.platform_timer = NULL;
> > >   		pr_err(FW_BUG "invalid timer data.\n");
> > >   		return -EINVAL;
> > >   	}
> > > -	acpi_gtdt_desc.platform_timer = platform_timer;
> > > +
> > >   	if (platform_timer_count)
> > >   		*platform_timer_count = gtdt->platform_timer_count;
> > > -- 
> > > 2.20.1
> > > 
> > .
> >